Coupling parts of this kind are known in a wide variety of types, in particular for hydraulic connections to be used in hydraulic systems. The removable fixation is usually achieved by means of a screw connection composed of an external thread on the coupling part and a matching internal thread in the corresponding receptacle, so that the known coupling parts, or the connections made by their means, may alternatively be referred to as screw couplings. The said first fluid-handling components are for example hydraulic connecting or extension lines in the form of pipe or tubing. The said second fluid-handling components are hydraulic elements such as for example hydraulic cylinders, junction blocks, valves or the like. A screw coupling basically has the advantage of high reliability and dependability in service, combined with the advantage that the connection may at need, for example for purposes of repair, be sundered with a suitable tool. The disadvantage of a screw coupling, or screw connection, consists essentially in the relatively great assembly effort involved in making the connection, which in many fields, including for example automobile manufacturing, conflicts with the requirements of production efficiency.
In hydraulic applications, where as a rule very high hydraulic pressures, for example on the order of up to 250 bars and more, are employed, the coupling part must be expected not only to make a secure and faultless connection, but also to be of such configuration that the connection is positively assured, any defects in the connection being ruled out.